Which starting material used in the air bag inflator is least important for the proper inflation of the air bag? Would it be necessary to have it present in a precise stoichiometric ratio? Why or why not?
2. What is the correct stoichiometric ratio between NaN3 and KNO3 to ensure no sodium is unreacted? What would be the consequences of an excess of KNO3 to the operation of an air bag?
To determine which starting material used in the air bag inflator is least important for proper inflation, we need to understand the role of each chemical and their potential consequences if not present in the proper ratio.
1. The main components involved in the inflation of an airbag are sodium azide (NaN3) and potassium nitrate (KNO3). NaN3 is typically used as the primary propellant, while KNO3 acts as an oxidizer.
NaN3 serves as the critical component in the inflation process. When the airbag sensor detects a collision, an electric signal is sent to ignite a small amount of NaN3. This initiates a chemical reaction that rapidly decomposes NaN3 into nitrogen gas (N2) and sodium metal (Na). The high-pressure nitrogen gas then inflates the airbag rapidly, providing cushioning and protection to occupants.
On the other hand, KNO3 is used to provide additional oxygen to support the combustion of sodium metal. It helps ensure complete combustion of sodium, preventing the formation of any sodium byproducts, which could be hazardous to occupants.
2. The stoichiometric ratio between NaN3 and KNO3 must be carefully controlled to avoid any unreacted sodium. The correct stoichiometry between NaN3 and KNO3 is 6:4, meaning six moles of NaN3 react with four moles of KNO3. This balanced ratio ensures that all sodium (Na) is consumed during the chemical reaction, and no unreacted sodium remains.
If there is an excess of KNO3 (an improper stoichiometric ratio), it would hinder the operation of the airbag. Excess KNO3 would lead to insufficient amounts of sodium available for reaction, resulting in incomplete combustion and the formation of unreacted sodium. Unreacted sodium can be highly reactive and dangerous, causing violent reactions and potential harm to the vehicle occupants.
In conclusion, while both NaN3 and KNO3 play important roles in inflating the airbag, NaN3 is the least important starting material for proper inflation, as its main purpose is to rapidly generate nitrogen gas. However, the presence of KNO3 in the correct stoichiometric ratio is crucial to ensure complete combustion of sodium and prevent the formation of unreacted sodium, which can pose a safety risk.